Important Questions with Answers for CBSE Board – 2019

Question 2: Mention one negative effect of our affluent life style on the environment. Answer 2: Excessive use of fossil fuel, even when we have to go nearby we use car, motor cycle, etc. instead going on foot or by cycle. Fossil fuels, on burning produce oxides of carbon, nitrogen and sulphur which cause air pollution.

Question 3: Distinguish between biodegradable and non-biodegradable substances. List two effects of each of them on our environment. Answer 3: Biodegradable: (i) They can be broken into simplest form by biological processes. (ii) They do not produce more pollution. (iii) They remain for less time in environment. Non-biodegradable: (i) They cannot be broken by biological processes. (ii) They produce more pollution. (iii) They remain for a long time in the environment. Effect of biodegradable substances: (i) They release harmful gases like methane. (ii) They release foul smell. Effect of non-biodegradable substances: (i) They are very harmful for the various member of the ecosystem. (ii) They cause more pollution of air, water and soil.

Question 4: Why is energy flow in the biosphere unidirectional? Answer 4: The sun is the only source of energy which plants trap during photosynthesis and store as food. The transfer of energy from one trophic level to the other obeys 10% law, i.e., 90% of energy is lost as heat. The energy in the form of heat goes unutilised because plants cannot use this heat energy in the synthesis of food. Thus, there is always flow of energy from the non-living component (then sun) and is released as heat. So, the energy flow in the biosphere is unidirectional.

More Questions for Exams

Question 1: Explain the phenomenon of “biological magnification”. How does it affect organisms belonging to different trophic levels particularly the tertiary consumers? Answer 1: When any harmful chemical like DDT, BHC enters in a food chain the concentration of chemical increases as the trophic level is increased (i.e., next higher level). The phenomenon is called biological magnification. These chemical, get accumulated progressively at each trophic level. It is maximum at the top (highest) trophic level. The tertiary consumers occupy the top trophic level (in most of the food chains) so there is maximum concentration of the harmful chemicals ant they are affected badly.

Question 2: What is an Eco-system? Answer 2: Eco-system is the whole biotic community (living organisms) in a given area plus its abiotic environment (physical factors like temperature, rainfall, wind, soil and minerals) both interacting with each other and maintain a balance in nature. Eco-system can be as large as a forest, or small as a pond or lake. This functional system may be natural as forest or may be artificial (man-made), e.g., a crop field or an aquarium. Thus the Eco-system has biotic and abiotic components.

Question 3: The flow of energy in food chain is unidirectional. Why? Answer 3: The flow of energy in a food chain follows 10% law. The energy used or lost in environment as heat, cannot enter at any trophic level in the food chain. Only solar energy can enters in the food chain at producer level and ultimately get lost as heat.

Question 4: What is ozone and how it affect any Eco-system? Answer 4: Ozone(O3) a molecule formed by three atoms of oxygen. It is a deadly poisonous gas. However, at the higher level of atmosphere, it performs an essential function. It shields surface of earth from ultraviolet radiation (UV) of solar radiations. This radiation is highly damaging to organisms, it is known to cause skin cancer, cataract in human beings.